Dam



l mas -w Feb. 23 11932. s. w. STEWART DAM Filed April 30, 1930 2Sheets-Sheet l INVENT xk ATTORNEY Feb. 23, 1932. s, w, STEWART 1,846,840

DAM

Filed April 1930 2 Sheets-Sheet 2 Patented Feb. 23, 1932 1 UNITEDSTATES- PATENT; FFICE srnncnn w. STEWART, or WHITE PLAINS, NEWyonn'assrenon. To annunsnn oo t- STRUGTION COMPANY, IN'C., on NEW YORK,I\1'.Y., A conronarron" on NEW YORK Application filed April 30,

This invention relates to a novel and im proved form'of dam and moreparticularly to a foundation therefor. The novel features will be bestuderstoocl from the following description and the annexed drawings, inwhich are shown selected embodiments of the invention and in which:

Fig. '1 is a fragmentary I sectional View through a dam lengthwisethereof, and illustrating prior art practice.

Fig. 2 is a View corresponding to Fig. 1 but showing the practiceaccording to one embodiment of my invention.

Fig. 3 is a verticalsectional view through a dam, this section beingtaken at right angles to the plane of Fig. 2.

Fig. 4. is a view similar to Fig. 3 but'showing a different embodimentof the invention.

Fig. 5 is a View corresponding to Fig. 2 but illustrating the inventionas practiced accordingto the embodiment shown in Fig. 4.

Fig. 6 is'a view on the same plane as Fig. 5' but on an enlarged scale.V

Fig. 7 is another View onthe same plane as Figs. 5 and 6 but on a stilllarger scale, to illustrate the details ofthe construction.

At certain sites selected for the construction of dams there isfrequently found an area or areas comprising foundation material notcapable of taking the full loading put upon it by thedam structure. Suchareas frequently occur at portions of a site. which is otherwise ofexcellent material for dam construction. Examples of such areas arefurnished by rock, which is different in character from the high-graderock adjacent it or rock which may be broken or have lines of cleavagenot capable of resisting the sliding forces put upon it by the weight ofthe structure; 'a' faulted condition caused by earthquakes or majorearth movements; or a deep narrow gorge filled with earth or other softmaterial which it would be uneconomical to excavate. V

An example of a situation which may be found is shown in Fig. 1, whereinA designates a portion of soft material which may be found in the streambed across which the dam is being built and which may extend downwardlyfor a great depth. Adjacent 1930. Serial No. 448,459.

this material may be found a portion B of" broken rock capable of takingmore'load than the portionA but still not suflic-iently. good to supportthe dam structure. On opposite sides of the poor material A and B thisuncertainty as to the support from beneath, and usually they are inactual practice far in excess of those for which the founda tionstructure was designed, or could be de-. signed economically. The resultis, of course,

a dangerous condition which may jeopardize the entire structure.Anothertype of fault is also illustrated in Fig. 1, this fault beingexemplified by'theline-of cleavage, F which often occurs with acondition such as shown in Fig. 1, and may, of'course, occur independwently of the veins of poor foundation material A and B; This plane ofcleavage F slopes towards the river bed and represents a fractureunderlying a considerable portion of the dam structure. When the dam isunder load, there is seriousdanger that the portion of the structureover the plane F will slide toward the river bed under the influence ofthe lateral forces induced by the weight of the structureover'theseplanes. This condition has been a serious menace to damsconstructed under prior art practice and, so far as I know, nosuccessful and economical way of resisting it has been devised.

Referring now to Figs-:2 and 3, I have shown therein one embodiment ofthe invention in which it is possible to economically build a foundationfor a dam superstructure which will overcome the difficulties discussedabove. In this form, I span the river bed or portion containing the poorfoundation mateif rial A and B by a monolithic plug 1 resting on thematerial A and B and also on the sound rock C on opposite sides of thismaterial. The top 2 of this plug is formed as an eXtrados of an arch andthe theoretical intrados is indicated by the dotted line 3. The plug isso designed thatthearch 4:. disposed between the lines 2 and 3 isnormally capable of supporting the superstructure of the dam disposedabove it. It is well known that a beam which is short as compared withits thickness, will have an interior arch action and I make use of thatprinciple in this construc tion. The portion of the plug beneath theline 3 will rest upon the material and B and when the load is thrustupon the plug from the superstructure of the dam, the tendency is forthe arch to deflect, thus setting up tensile stresses at the under sideof the arch. and in the plug beneath the arch. In Fig. 2, I have shownlines ,5 which indicate construction joints and which may be disposedsubstantially radially of the arch so as to divide the arch into whatare in effect a plurality of voussoirs. As the arch deflects, thesejoints may open up to a certain height, but the structure is so designedthat they will not open within the limits of the theoretical arch. Atthe same time, the material A and B will normally be sufficiently goodfoundation material to support the masonry in the plug beneath the line3 and may be good enough to provide some support for the masonry in thearch itself and thus aid the arch in supporting the superstructure ofthedam. The conrial A and B is ignored, except in so far as r it isconsidered sufficient to support the concrete below the line 3. r

In order to aid in preventing slides such as might occur along thecleavage plane-F, I provide a plurality of bracing walls 6 eX- tendingtransversely of the arch or lengthwise of the dam, these walls extendingbetween the buttresses 7 of the superstructure, these buttresses in turnsupporting the water bearing member 8. It is preferable to form theextrados of the arch in steps, as indicated in Fig. 2, and to providesliding joints 9 between the bracing walls and the arch. Otherwise, anadditional stress would be induced in the bracing walls by the load andpossible deflection of the arch. It is preferable to have the top 10 ofeach wall in the same horizontal plane and to make each wallsubstantially continuous to the bearing material on each bank of thestream. The banks may be further braced against lateral movement bypouring monolithic concrete between the ex trados and the bank, asindicated at 11.

Referring now to Figs. 4, 5, 6 and 7, I have shown an arrangementsomewhat similar to what has been just described, except that here thearch 12 is separate from the subintradosal concrete 13, this concretebeing placed between the intrados 14 of the arch and the bed of thestream exemplified by the top of the material A and B. The arch is carried completely across the material A and B to solid rock at G and onits extrados 15 it supports the superstructure of the dam, hereindicated as buttresses 7 supporting the deck 8. The bracing walls (Sandmonolithic concrete 11 may be used here as in the other embodiment, totake up side thrust,as from material above the fault F.

The load on the dam constructed according to this embodiment will causea deflection of the arch 12, but as this arch is in direct contact withthe sub-intradosal concrete beneath it, the tendency to deflect isresisted by this concrete, and the material A and B thus is permitted tocarry all of the load that it can. The remainder of the load will betransmitted in direct thrust to the solid material at the abutments ofthe arch. If the load on the dam is removed, the'sub-intradosal concretemay or may not rise as the load returnsto its initial position. When thedam is again loaded, however, the arch will dew fleet and again come incontact with the upper surface of this sub-'intradosal concrete.

In designing the arch of this embodiment, care should be taken toprevent adhering of the sub-intradosal concrete 1? to the intrados ofthe arch, because this would prevent the functioning of the structure asdesigned. The bond between the arch and the sub-intradosal concrete maybe prevented by. coating the surface of one or both with some materialsuch as oil or a thin asphalt paint.

In the form shown in Figs. 4, 5, 6 and 7, there must be considered theefiect of back water loading that may occur when a structure of thistype is placed in a river bed section. According to this invention, backwater is permitted to pass from the extrados to the space between theintrados and the top of the sub-intradosal concrete, whichmay be formedby deflection and subsequent rising of the arch, or by settlement ofthesub-intradosal concrete. The water may be admitted by means of drainpipes 16 through the arch or by inlets 17 which are here shown in theform of grooves inthe upper surface of the sub-intradosal concrete,which grooves run transversely of the arch. The ends of the pipes 16 aredisposed in these grooves which may conveniently be filled with porousmaterial 18. These fillers may be formed of porous mortar which'willpermit water to pass lengthwise of the grooves and thus a pressure ispermitted. to build up on the intrados of the arch, which pressure willbe equal to the pressure from the water on the extrados. Thisarrangement provides equal pressure on both sides of the arch andtherefore will I lighten the weight of the arch barrel to a certainextent. I

I claim z- 1. A masonry dam extending across an area of poor bearingmaterial beneath it and having a foundation formed of an arch extendingacross said area with its abutments on solid material on opposite sidesof said area, a superstructure supported at least in part on said arch,and masonry closing the space beneath the intrados of said arch, wherebydeflection of the arch will transfer part of the load on the arch tosaid masonry and thence to said poor bearing material.

2. A masonry dam extending across a depression in the ground andcomprising a superstructure, a foundation supporting said superstructureand comprising an arch extending across the lowest part of saiddepression, means closing the space beneaththe intrados of said arch,and walls extending from said arch to the material on the sides of thedepression to transmit thrust to the arch from said material. a

3. A masonry dam extending across a depression in the ground andcomprising a superstructure, a foundation supporting said superstructureand comprising an arch extending across the lowest part of said depression, means closing the space beneath the intrados of said arch, andmasonry disposed between said arch and the material on the sides of thedepression to transmit thrust from said material to the arch.

4:. A masonry dam extending across an area of poor bearing materialbeneath it and having a foundation formed of an arch extending acrosssaid area with its abutments on solid material on opposite sides of saidarea, masonry closing the space, beneath the intrados of said archwhereby deflection of the arch will transfer part of the load on thearch to said masonry and thence to said poor bearing material, and meanspreventing the sub-intradosal masonry from forming a joint with themasonry in said arch, whereby the arch may act independently of saidsubintradosal masonry. V

5. A masonry dam extending across an area of poor bearing materialbeneath it and having a foundation formed of an arch extending acrosssaid area with its abutments on solid material on opposite sides of saidarea, masonry closing the space beneath the intrados of said arch, andmeans for admitting back water to the space between the intrados of thearch and the top of the sub-intradosal masonry.

SPENCER W. STEWART.

